Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$184.51	8.579%	$200.3391	$200.34	$200.35	$200.30
Purchase #2	$167.50	10.329%	$184.8011	$184.80	$184.80	$184.80
Purchase #3	$60.41	5.434%	$63.6927	$63.69	$63.70	$63.70
Purchase #4	$151.25	13.721%	$172.003	$172.00	$172.00	$172.00
Purchase #5	$138.60	9.441%	$151.6852	$151.69	$151.70	$151.70
Purchase #6	$241.39	9.558%	$264.4621	$264.46	$264.45	$264.50
Purchase #7	$36.37	6.607%	$38.773	$38.77	$38.75	$38.80
7 purchase totals =	$980.03		$1,075.7562	$1,075.75	$1,075.75	$1,075.80